This invention relates in general to agricultural equipment and in particular to a combine for harvesting and threshing grain using an axial flow threshing and separating means.
Self-propelled combines for harvesting and threshing grain such as wheat have been available for many years. These combines are large devices having a frame mounted on wheels. A header, often 14 to 30 feet wide, cuts the crop and forces it inwardly into a threshing means. The threshing means includes a cylinder with protruberances such as rasp bars that are rotated closely past a grate. The feed may be tangential or axial into the cylinder. Some of the cylinders are flared or conical. Grain threshed from the crop is conveyed into a sieve means which normally has primary and secondary sieves for removing chaff and returning tailings. The sieves are screens with inclined fingers, the screens being shaken to cause the clean grain to fall through. A blower blows air across the sieves to discharge the chaff. Tailings, which are too heavy to be blown out, but too large to fall through the fingers, are returned for further threshing to remove the grain from the debris of the crop.
After threshing, the crop debris, such as the straw, is pushed out by various means and discharged. The clean grain from the sieve is conveyed up to a storage bin on top of the combine, normally by paddles mounted on a chain. When the bin is full, the grain is conveyed into a track or trailer by means of an auger connected to the bin.
While successful, the large number of moving parts makes these combines expensive. The complexity also makes the combines subject to frequent failure. There are many bearings, V-belts, pulleys, chains and the like. Another problem occurs when the combine tilts transversely or sideways on a hill. This tends to load up one side of the sieves. Unless the operator slows the machine, grain is likely to be blown out and wasted. Slowing down the machine might avoid wastage of grain, but results in lower productivity for the combine. Combines with means for leveling portions of the combine to avoid this problem are available. However, the hydraulic systems used are complex and expensive.